DOPPLER ECHOCARDIOGRAPHY IN THE NORMAL DOG: PART I VELOCITY FINDINGS AND FLOW PATTERNS

This study examined the blood flow velocities and flow patterns in the normal dog using pulsed wave spectral Doppler echocardiography in eight areas of the heart. Two breeds of dogs, aged between 8 and 112 weeks and of both sexes, were used. The dogs were fully conscious and no drugs were used. The areas examined were the mitral valve, left atrium, tricuspid valve, right atrium, aorta, left ventricular outflow tract, pulmonary valve and the right ventricular outflow tract. The peak and mean velocities, direction of flow and whether flow was systolic or diastolic was determined for each of these flow areas. Additionally each of these waveforms were described. Aortic flow was also measured from the thoracic inlet by continuous wave Doppler.     

QUANTITATIVE CROSS-SECTIONAL ECHOCARDIOGRAPHY IN THE NORMAL DOG

Two-dimensional echocardiography was performed on 18 unanesthetized, normal dogs (4.5 to 30 kg). Measurements of wall thickness, intracavitary dimensions, and cross-sectional area of the left atrium, left ventricle, and aorta were made. Satisfactory data were obtained from 17 dogs, and were used to determine normal values. Normal data were tested for significant correlation to body weight (kg) by linear regression. Repeatability was studied in six dogs examined, on three separate occasions, during a 5-day period. Differences between values obtained on different days were evaluated by analysis of variance.
Satisfactory qualitative echocardiograms were repeatedly obtained by using consistent sites of transducer placement and by identifying internal cardiac structures. These tomographic planes were highly reproducible, with only ventricular length, and some views of the ventricular septum, showing statistically significant (P < 0.05) differences. Almost all linear and area measurements were significantly correlated to body size, while most indices of left ventricular function were independent of body weight. Dimensions obtained from the left and right parasternal position were nearly identical. Cross-sectional echocardiography allows repeatable assessment of cardiac anatomy, and it should prove useful for identification and quantitation of heart disease in the dog.     

DOPPLER ECHOCARDIOGRAPHY IN THE DOG: MEASUREMENT VARIABILITY AND REPRODUCIBILITY

Serial Doppler echocardiographic examinations were carried out in random order on six boxer dogs, on 3 separate days, by two experienced Doppler echocardiographers, to assess measurement variability and reproducibility of 65 parameters. Large numbers of parameters exhibited significant differences for each of the categories of intraobserver, interobserver, interday and interoperator. The coefficients of variation for all parameters measured ranged from 5.03 to 46.43%, but most were less than 20%. In general, least variation was found for the intraobserver category, and the best reproducibility for M-mode and left ventricular volumetric data. The worst reproducibility was found for tricuspid inflow and pulmonary venous flow measurements. The results of this study suggest differences greater than 20% for serial scans must be achieved to document genuine change, although the specific data should be consulted. Furthermore, variability and reproducibility are improved if a single experienced operator/observer acquires and measures serial scans.     

BIPLANE TRANSESOPHAGEAL ECHOCARDIOGRAPHY IN THE DOG: TECHNIQUE, ANATOMY AND IMAGING PLANES

To determine the feasibility of transesophageal echocardiography (TEE) in dogs, biplane TEE was performed in 6 normal, anesthetized dogs, using a 10 mm × 110 cm endoscopic TEE transducer. Positioning was confirmed by fluoroscopy, and imaging planes were confirmed by necropsy examination.
A transgastric position provided only a limited view of the left ventricular apex. Three TEE positions over the base of the heart were identified. A caudal position provided excellent images in both transverse and longitudinal planes, but alignment with flow for Doppler examination was poor. A middle position provided long axis views of the left ventricular inflow region and mitral valve suitable for Doppler examination. A cranial position provided excellent views for both anatomic and Doppler examination of right and left ventricular outflow and associated great vessels.
We conclude that biplane TEE provides unique views of the heart in dogs which are complementary to, and often superior to, transthoracic views for evaluation of structures at the heart base.     

ECHOCARDIOGRAPHIC INDICES IN THE NORMAL DOG

Twenty young healthy dogs weighing from 9.8 to 28.6 kg were studied by M-mode echocardiography. Parameters were measured and statistically evaluated to determine whether a correlation to body surface area existed. A statistically significant correlation to body size was found for the aortic, left atrial, left ventricular, septal, and posterior wall dimensions and the mitral valve amplitude of motion. In addition, normal values not correlated to body surface area are presented with their means and standard deviations. These values include velocity of circumferential fiber shortening, ejection time, percent systolic thickening of septum and posterior wall, percent change in minor diameter, selected dimension ratios, and mitral valve velocities     

BIPLANE TRANSESOPHAGEAL ECHOCARDIOGRAPHY IN THE NORMAL CAT

Eight healthy, adult cats were examined with biplane transesophageal echocardiography (TEE). Cats were sedated with a combination of diazepam and propofol and were examined using a 5 mm x 80 cm pediatric biplane TEE probe. Consistent images were obtained at three imaging depths within the esophagus. The middle position porvided the best short-axis images of the left ventricle andheart base. The middle position provided the best long-axis views of the left atrium, left ventricle, and aorta satisfactory imaging of the aorta and pumonary artery and allowed Doppler examination of right ventricular and left ventricular outflow. Biplane TEE provides and additional method of imaging the feline heart which is complimentary to other imaging techniques and the images obtained were similar to those reported for dogs. Although TEE offers a slight advantage over transthoracic imaging for Doppler examination, the quality of the images of heart base structures was not as consistently superior to transthoracic images in cats as reported in dogs.     

TESTICULAR ULTRASOUND IN THE NORMAL DOG

The testicles of ten dogs presented for routine castration were imaged with real time ultrasound. A scanning technique using multiple imaging planes (sagittal, transverse, and dorsal planes) was developed to image the testicles and epididymi. The testes were characterized by a coarse medium echo pattern. The mediastinum testis was consistently seen as a 0.2 cm wide linear hyperechoic structure in the central long axis of the testis. The ability to identify and the appearance of the epididymis was variable. The tail was consistently seen as an anechoic to hypoechoic structure. Ultrasound images were compared for anatomical structure with frozen gross sections. Ultrasonic and gross measurements were made and analyzed. Individual gross and ultrasonic measurements compared favorably. Linear regression coefficients between body surface area versus testicular length and diameter were 0.73 and 0.58 respectively. A Wilcoxin signed rank test for similarity p = 0.33 value was found when comparing the right to the left testicle.     

TWO-DIMENSIONAL, REAL-TIME ECHOCARDIOGRAPHY IN THE DOG Technique and Anatomic Validation

Two-dimensional, real-time echocardiography (2DE), studied extensively in humans, has only recently been utilized in veterinary medicine. To develop standardized transducer locations and examination technique and to validate cardiac anatomy as imaged from these locations, 2DE was performed in 12 normal, anesthetized dogs. Anatomic structures were identified by shape, position and motion, selective microbubble-laden saline injections, and percutaneous pin insertion followed by necropsy dissection. Consistent echotomographic images were obtained from right intercostal and left intercostal transducer locations. From the right, long-axis and short-axis views of the heart were obtained. From the left, several long-axis views were possible. One or more views of all four cardiac chambers, atrioventricular and semilunar valves, and the proximal portions of the great vessels were obtained by systematic examination from both sides of the thorax. It was concluded that complete anatomic evaluation of the canine heart by 2DE was possible using a standardized, systematic examination technique.     

ECHOCARDIOGRAPHIC AND DOPPLER CHARACTERISTICS OF POSTOPERATIVE DUCTAL ANEURYSM IN A DOG

A patent ductus arteriosus (PDA) was detected in a 10-month-old Pyrenean Shepherd. The PDA was occluded with hemostatic clips. One month after surgery, an aneurysmal dilatation of the ductus was diagnosed using Doppler echocardiography. The authors present the echo-Doppler findings and the follow-up of the ductus aneurysm. The pathogenesis and significance of such an aneurysm are discussed.     

PULMONARY VENOUS FLOW CHARACTERISTICS AS ASSESSED BY TRANSTHORACIC PULSED DOPPLER ECHOCARDIOGRAPHY IN NORMAL DOGS

Transthoracic Doppler echocardiography was used to evaluate the technique of measuring and normal patterns of pulmonary venous flow in fourteen normal dogs. Polyphasic pulmonary venous flow profiles were obtained in all dogs, consisting of one (S) or two (S_E and S_L) systolic forward flow waves, one early diastolic forward flow wave (D), one reverse flow wave (R) related to atrial contraction, and one reverse flow wave (R₂) observed after cessation of systolic flow. Pulmonary venous flow was laminar in 9 dogs (65%). Maximal flow velocity during systole (0.39 ± 0.14 m/sec) was significantly lower (P < 0.01) than in early diastole (0.56 ± 0.14 m/sec). During late diastole peak flow velocity was 0.20 ± 0.08 m/sec and maximum R₂ velocity was 0.17 ± 0.05 m/sec. Duration of mitral A-wave was significantly greater (P < 0.05) than R-wave duration in all dogs (0.075 ± 0.10 vs 0.058 ± 0.012 sec). These results can be used for comparison with patterns found in disease states.     

EPIDUROGRAPHY IN THE NORMAL DOG: TECHNIC AND RADIOGRAPHIC FINDINGS

Ten clinically normal adult mongrel dogs were examined using lumbosacral epidurography in an effort to determine a reproducible technic and a normal radiographic appearance. The site of contrast medium injection was the ventral epidural space at the sacrococcygeal junction or the cranial coccygeal region. An initial dose of 0.15 ml/kg of metrizamide for the right lateral recumbent radiograph with 0.10 ml/kg additional metrizamide for additional right lateral or the subsequent dorsoventral radiographs was considered adequate. Two numerical values were observed for each normal epidurogram: the sacrovertebral angle; the ratio of the contrast medium column width to L6 body length. A statistically significant relationship between hindlimb positioning and the numerical value of the sacrovertebral angle was identified. Some advantages of epidurography for delineating the lumbosacral area are obvious: (1) it overcomes the limited value of lumbosacral area myelography; (2) it is technically easier than intraosseous vertebral venography; (3) there is minimal patient trauma; (4) there was no apparent adverse sequela to repeated contrast medium injections.     

M-MODE ECHOCARDIOGRAPHIC PARAMETERS AND INDICES IN THE NORMAL GERMAN SHEPHERD DOG

M-mode echocardiographic measurements were made from 50 healthy German Shepherd dogs (30 males and 20 females). The dogs were awake and unsedated, in right lateral recumbent position. The following parameters were measured on the echocardiographic images: interventricular septal thickness at end-diastole (IVSd), interventricular septal thickness at end-systole (IVSs), left ventricular internal dimension at end-diastole (LVIDd), left ventricular internal dimension at end-systole (LVIDs), left ventricular posterior wall thickness at end-diastole (LVPWd), left ventricular posterior wall thickness at end-systole (LVPWs), left atrial dimension (LAD), aortic root dimension (AOD), left atrial to aortic root ratio (LAD/AOD), right ventricular internal dimension at end-diastole (RVID), amplitude of mitral valve excursion (DE amplitude), velocity of mitral valve opening (D-E slope), and velocity of mitral valve closure (E-F slope). Fractional shortening (FS) was also calculated. The effect of gender and age on each echocardiographic parameter was analyzed and the relationship between body weight (BW) and each parameter was also investigated. There was a significant relationship between gender and LVPW in systole and diastole and FS. Significant association was also found between BW and IVS, LVID, and LVPW in systole and diastole, FS, LAD, AOD, RVID, DE amplitude, and D-E slope of the mitral valve.     

DOPPLER ULTRASOUND OF THE PROSTATE IN NORMAL DOGS AND IN DOGS WITH CHRONIC LYMPHOCYTIC-LYMPHOPLASMOCYTIC PROSTATITIS

The prostate gland of 11 normal dogs and five dogs with histological confirmed chronic lymphocytic or lymphoplasmocytic prostatitis were imaged with grey-scale and Doppler ultrasound. Three vessel types (prostatic artery, capsular artery and parenchymal artery) were identified with color Doppler and the resistive index and maximum and minimum velocities were measured with pulsed wave Doppler. No differences between normal dogs and dogs with prostatitis was identified in either grey-scale ultrasound or in any Doppler parameters measured. Regardless of histologic diagnosis, acepromazine (0.05 mg/kg IV) caused a significant decrease in capsular artery maximum and minimum velocities and prostatic artery resistive index. This study establishes normal Doppler ultrasound parameters for the intact male canine prostate gland. Additional studies are necessary to further evaluate the clinical utility of Doppler ultrasound in canine prostatic diseases.     

PNEUMOPERICARDIOGRAPHY IN THE NORMAL DOG

To define the normal radiographic anatomy of the canine heart and pericardial space as outlined by air, pneumopericardiography was performed in ten normal, anesthetized dogs using a percutaneously introduced pericardial catheter. Room air was injected to produce pneumopericardiums without causing cardiac tamponade, and radiographs were obtained using a vertical beam with the dogs positioned in right lateral (RLAT), left lateral(LLAT), dorsal (VD), and ventral (DV) recumbency. Selective and nonselective angiocardiography was used to confirm the identity of the outlined structures. The RLAT and LLAT positions provided more information than the DV or VD positions. Pericardial air consistently outlined a distinct interventricular sulcus and the recesses around the aorta and pulmonary artery. The right auricle, outlined along the cranial heart border ventral to the ascending aorta in both RLAT and LLAT positions, varied considerably in size. The RLAT position best outlined structures to the left of midline, including the left auricle, interventricular sulcus, outflow region of the right ventricle, and the origin of the pulmonary artery. The LLAT position best demonstrated structures to the right of midline, including the right atrium, proximal part of the cranial and caudal vena cavae, and ascending aorta. The considerable range of normal variation between dogs in this study must be considered in the interpretation of clinical pneumopericardiograms.     

COLOR DOPPLER AND DOPPLER SPECTRAL ANALYSIS IN THE SPINAL CORD OF NORMAL DOGS

Doppler ultrasonography of the spinal cord was performed in 34 normal, anesthetized dogs following hemilaminectomy. This study was part of an investigation to evaluate the efficacy of a 21-aminosteroid compound and high dose methylprednisolone for the treatment of spinal cord trauma. Grey-scale images of the canine spinal cord were similar to those described for the spinal cord of people. Doppler waveforms of intraparenchymal spinal arteries exhibited high end diastolic blood flow velocities, indicating low resistance to flow. Doppler values (mean ± SD) for arteries immediately ventrolateral to the central canal were: Peak Systolic Velocity = 5.78 ± 2.5 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Minimum Diastolic Velocity = 3.5 ± 1.62 cm/sec, Mean Velocity = 4.45 ± 1.96 cm/sec, Systolic/Diastolic ratio = 169 ± 0.19, Pulsatility Index = 0.53 ± 0.09, and Resistance Index = 0.4 ± 0.06.     

ESTIMATION OF PORTAL BLOOD FLOW USING DUPLEX REAL-TIME AND PULSED DOPPLER ULTRASOUND IMAGING IN THE DOG

A duplex ultrasound system incorporating a pulsed wave Doppler ultrasound probe with conventional B-mode real-time imaging was used to evaluate portal vein blood flow in eight normal dogs. Adequate visualization of the cranial abdominal vessels was obtained from the right lateral 11th or 12th intercostal space. Doppler spectral analysis showed non-pulsatile flow with a wide range of linear flow velocities across the vessel lumen typical of laminar blood flow. Results for portal vein blood flows were 49.8 ± 13.5 ml/min/kg body weight (mean ± SD) with a range of 37.8 - 76.8 ml/min/kg body weight. These values overestimate portal blood flow by approximately 2 times when compared with published studies using invasive techniques. This overestimation is primarily due to the use of the maximal flow velocity in the blood flow calculations.     

DOUBLE CONTRAST GASTROGRAPHY IN THE NORMAL DOG

Double contrast gastrography affords more accurate detection of gastric lesions because it allows direct evaluation of mucosal pattern contours. The technic involves the induction of gastric hypomotility with intravenous glucagon, gastric intubation for the introduction of air and high-density barium directly into the stomach, and positional manipulation for maximal air-barium interface demonstration. Some dogs require sedation. Although fluoroscopic observation is an asset in isolating gastric anatomic abnormalities, this study may be performed using conventional radiographic equipment without fluoroscopic guidance. Double contrast gastrography is used to demonstrate the stomach mucosal surface by coating it with high-density barium and having the mucosa contrast with the air-filled gastric lumen. There are three elements to each double contrast image: the dependent surface, the nondependent surface, and the barium pool. The barium pool is manipulated to coat the mucosal surface and fill depressions of the dependent surface. Protrusions of the dependent surface appear as radiolucencies in the barium pool. Depressions and protrusions of the nondependent surface are outlined by barium. Double contrast gastrography is indicated in dogs where clinical signs suggest anatomic changes in the gastric mucosal surface, e.g., neoplasms, ulcers, or polyps. Concurrent gastrointestinal motility evaluation is precluded by sedation and the glucagon-induced gastric hypomotility.     

GASTRIC EMPTYING IN THE NORMAL DOG A Contrast Radiographic Technique

A total of 22 radiographic studies was made to determine comparative gastric emptying times of two different solid test meals (intact kibble food and ground kibble food mixed with barium sulfate suspension) in four mature (15-26 months) normal Beagle dogs under controlled conditions. Complete gastric emptying times of the intact kibble and ground kibble meals of a given dose (8 g/kg of dog food plus 5-7 ml/kg of the contrast agent) ranged from five to ten hours (7.6 ± 1.98 hours with intact kibble meal and 7.0 ± 1.86 hours with ground kibble meal). Feeding a halfdose of ground kibble meal (4 g/kg of dog food plus 3.5 ml/kg of the contrast agent) resulted in complete gastric emptying times of four to six hours (4.7 ± 0.67 hours). Individual dogs had repeatable gastric emptying times although the times varied among different dogs.     

ULTRASONOGRAPHIC EXAMINATION OF THE PHARYNX AND LARYNX OF THE NORMAL DOG

Real-time ultrasonographic examination of the canine larynx was performed in 12 normal dogs using a 7.5-mHz mechanical sector scanner combined with a stand-off. A variety of breeds and ages were examined. All examinations were performed in nonsedated, conscious animals. Transverse scans were found to provide the most reliable and interpretable images. Identification of laryngeal structures included the epiglottis, laryngeal and cricoid cartilages, and the vocal cords. In conscious animals, abduction and adduction of the vocal cords associated with respiration could be identified if the animal was made to pant during the examination. Movement of the vocal cords could also be quantified by pulse-wave Doppler recording. In all animals, recordings were made during inspiration only, with muscular vibration at a rate less than 0.1 m/s.     

M-MODE AND DOPPLER ECHOCARDIOGRAPHIC FINDINGS IN NORMAL FERRETS SEDATED WITH KETAMINE HYDROCHLORIDE AND MIDAZOLAM

M-mode and Doppler echocardiographic values were obtained from 30 normal adult ferrets (14 neutered females, 13 neutered males, 3 intact males) sedated with an intramuscular combination of ketamine hydrochloride and midazolam. Routine M-mode measurements of the left and right ventricle, left atrium (LA) and aorta (AO) and Doppler measurements of aortic and pulmonic outflow, and mitral inflow were recorded. The following values were calculated: LA:AO diameter, ratio of peak E: peak A wave velocity (E:A ratio) for mitral inflow, and stroke volume (SV), cardiac output (CO) and cardiac index (CI) for both pulmonary and aortic outflow tracts. Maximal aortic velocities (AOmax) and velocity-time integral values (AO VTI) were significantly less than corresponding pulmonary outflow tract values (PAmax, PA VTI) but there was no difference in calculated values for SV, CO or CI. Calculated CO values were in the range expected based on the size of the species. Difficulties in aligning the aortic outflow tract for Doppler imaging may make pulmonary outflow Doppler values more consistent for use in estimating volume flow in ferrets.